Multi-blade centrifugal fan

ABSTRACT

A multi-blade centrifugal fan, the fan arranged with a plurality of blades in round shape and equipped with an end plate mounted with a tip end of the plurality of blades, wherein the end plate is centrally mounted with protruded hub toward an air intake, and here a protruded height (Hb) of the hub is less than 0.3 times the outer diameter (Df), such that although a hub is mounted with a driving motor, an overall structural size is miniaturized to minimize a flow rate loss and to prevent a remarkable fan performance decrease.

BACKGROUND OF THE INVENTION

[0001] 1. FIELD OF THE INVENTION

[0002] The present invention relates to a multi-blade centrifugal fan, and more particularly to a multi-blade centrifugal fan adapted to miniaturize a system having a fan and a driving motor and to prevent a remarkable decrease of fan performance.

[0003] 2. DESCRIPTION OF THE PRIOR ART

[0004] Centrifugal fans, designed to induce air axially and to discharge the air circumferencially, are generally used for household package air conditions and the like.

[0005] This type of centrifugal fan includes a centrifugal multi-blade fan 4 radially formed with a plurality of blades 2 and a scroll casing 6 externally disposed at outside of the centrifugal multi-blade fan 4 to spirally form a draft passage, as illustrated in FIGS. 1 and 2.

[0006] The scroll casing 6 is mounted at axial direction of centrifugal multi-blade fan 4 with an air intake 8 for inducing the air, and the air intake 8 is formed with an air outlet 10 90 degrees relative to the air intake 8. The centrifugal multi-blade fan 4 is equipped with an end plate 12 installed at one side end of the plurality of blades.

[0007] The end plate 12 is centrally mounted with a hub protruding toward the air intake and the hub is formed at a space (S) thereof with a motor (M).

[0008] Elements that determine performance of a centrifugal fan include cut-off interval, shape of scroll casing, shape of blade and the like, and many studies to these elements serve to reduce noise and increase efficiency of the centrifugal fans.

[0009] A fan mounted on a household package air conditioner is formed with a hub protruded toward air intake at a central part of the end plate 12 in concert with miniaturization of household electric appliances, as illustrated in FIG. 2, and the hub is accommodated at the space (S) thereof with the driving motor (M) to thereby enable to reduce the overall size of the blower.

[0010] However, there is a problem in the fan thus described according to the prior art in that the protruded hub inevitably gives resistance to air inflow to decrease performance of the fan while there is provided no appropriate protrusion height for the hub for accommodating the motor as there have been no studies to protrusion height of the hub and performance of fan, prompting to make the fan assembly miniaturized but having to be ready to suffer decrease of the performance.

SUMMARY OF THE INVENTION

[0011] The present invention is provided to solve the aforementioned problems and it is an object of the present invention to provide a multi-blade centrifugal fan adapted to miniaturize a blower and to prevent a remarkable decrease of fan performance.

[0012] In accordance with the object of the present invention, there is provided a multi-blade centrifugal fan, the fan arranged with a plurality of blades in round shape and equipped with an end plate mounted with a tip end of the plurality of blades, wherein the end plate is centrally mounted with protruded hub toward an air intake, and here a protruded height (Hb) of the hub is less than 0.3 times the fan outer diameter (Df).

[0013] The hub is preferred to have a conical shape having a narrow diameter at air intake.

[0014] The hub may be shaped of a cylindrical form.

[0015] The hub is preferred to be formed at lateral surfaces thereof with an plurality of holes for cooling the heat of a motor disposed at a space of the hub.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] For fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings in which:

[0017]FIG. 1 is a schematic sectional view for illustrating a centrifugal fan according to the prior art;

[0018]FIG. 2 is a sectional view taken along line A-A of FIG. 1;

[0019]FIG. 3 is a perspective view of a multi-blade centrifugal fan according to a first embodiment of the present invention;

[0020]FIG. 4 is a schematic sectional view of a multi-blade centrifugal fan according to the first embodiment of the present invention;

[0021]FIG. 5 is a schematic sectional view of a multi-blade centrifugal fan according to a second embodiment of the present invention;

[0022]FIG. 6 is a graph for illustrating changed protrusion heights of hub at the multi-blade centrifugal fan of FIG. 4 for testing of fan performance; and

[0023]FIG. 7 is a graph for illustrating changed protrusion heights of hub at the multi-blade centrifugal fan of FIGS. 5 for testing of fan performance.

DETAILED DESCRIPTION OF THE INVENTION

[0024] Now, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0025] FIGS. 3 ad 4 illustrate the first embodiment of the present invention.

[0026] As shown in the drawings, a multi-blade centrifugal fan 20 is circularly formed with a plurality of blades 22, each at a predetermined interval while the plurality of blades 22 are mounted at one lateral end thereof (motor-attached side) with an end plate 24. The plurality of blades 22 are mounted at the other lateral end thereof (air intake side) with a support ring 26, rendering an entire look to be of a cylindrical shape.

[0027] The end plate 24 centrally protrudes toward an air intake to form a hub 28, where a protruded height (Hb) of the hub 28 is less than 0.3 times the fan outer diameter (Df). Diameter at air intake side of the hub 28 has a conical shape but rounded at corners thereof. The hub 28 may be integrally formed with the end plate 24 or may be formed with separate member.

[0028] The hub 28 is protrusively formed at an upper central surface thereof with a boss 30 for inserting and securing the axle of a motor (described later) while the boss 30 is mounted at an external surface thereof with a plurality of support ribs 32. The hub 28 is disposed at a space (S) formed thereunder with a driving motor (M) while a motor axle thereof is securely inserted into the boss 30. Furthermore, the driving motor (M) is supportively fixed at external surface or lower lateral surface thereof by scroll case (not shown) for encompassing the multi-blade centrifugal fan 20.

[0029] The hub 28 is formed at lateral sides thereof with a plurality of holes 34 for cooling the motor mounted at the space (S) of the hub. The support ring 26 is a fixed frame abutted on an external surface of the fan and maintains the plurality of blades 22 each at a predetermined interval for support.

[0030] Meanwhile, FIG. 5 illustrates a multi-blade centrifugal fan according to the second embodiment of the present invention.

[0031] A end plate 124 according to the present embodiment is cylindrical at a hub 128 thereof. The hub 128 is less than 0.3 times the fan diameter at protrusion height (Hb) thereof and rounded at corners thereof. Other constructions such as blades 122, supporting ring 126, boss 130, support rib 132, holes (not shown) formed at sides of the hub are the same as those of the first embodiment as shown in FIG. 4 (the first embodiment).

[0032]FIG. 6 illustrates performance result tests where, in a multi-blade centrifugal fan having a conical shape of hub, protrusion height (Hb) of the hub is changed from 0 times (hub not protruded), 0.25 times, 0.33 times, 0.48 times, to 0.59 times the fan outer diameter, such that FIG. 6 is a graph for showing a flow rate (φ: non-dimension) relative to static pressure (ψ: non-dimension)

[0033] The condition tested is as below:

[0034] 1. Testing device: Wind tunnel having a flow rate of 1.5˜50 m³/min, manufactured and designed in strict accordance to ASHRAE(American Society of Heating, Refrigerating and Air-conditioning Engineers)

[0035] 2. Testing method: Proceeded according to KSB6311

[0036] The multi-blade centrifugal fan having a conical hub used for the test has a fan height (Hf) 0.47 times the fan outer diameter (Df) while a maximum diameter (Db1) of the hub is 0.55 times the fan outer diameter (Df), a minimum diameter (Db2) is 0.51 times the fan outer diameter (Df) and width (Fw) of a blade is 0.09 times the fan outer diameter (Df).

[0037] As illustrated in the graph, it can be noted that multi-blade centrifugal fans, each having a protrusion height (Hb) of hub 0.25 times and 0.33 times the fan outer diameter (Df) respectively, almost approach a graph of a multi-blade centrifugal fan (Hb=0) of a hub not protruded.

[0038] The following table is a numerated graph of FIG. 6, where comparisions are given between flow rate (maximum flow rate) of a multi-blade having a zero protrusion height (Hb) of hub and flow rate decrease rate of protruded hub. Protrusion height of hub 0.25Df 0.33Df 0.48Df 0.59Df Flow rate decrease rate 2% 4% 8% 12% (against maximum flow rate)

[0039]FIG. 7 illustrates performance test results where, in a multi-blade centrifugal fan having a cylindrical shape of hub, protrusion height (Hb) of the hub is changed from 0 times (hub-not-protruded state), 0.30 times, 0.41 times, 0.55 times and 0.66 times the fan outer diameter (Df), such that FIG. 7 is a graph for illustrating a flow rate (φ: no dimension) versus static pressure (ψ: no dimension).

[0040] The testing device and method are the same as those of the multi-blade centrifugal fan having a conical shape of hub, where the multi-blade centrifugal fan mounted with a cylindrical shape of hub used for the test has a fan height (Hf) 0.47 times the fan outer diameter (Df) while diameter (Db) of the hub is 0.51 times the fan outer diameter (Df) and width (Fw) of a blade is 0.09 times the fan outer diameter (Df).

[0041] As illustrated in the graph, it can be noted that a multi-blade centrifugal fan disposed with a hub protrusion height (Hb) 0.30 times the fan outer diameter (Df) nearly approaches a graph of a multi-blade centrifugal fan having a hub of no protrusion (Hb=0).

[0042] The flowing table is a numerated graph of FIG. 7 where a flow rate decrease rate of protruded hub is given against flow rate (maximum flow rate) of a multi-blade centrifugal fan having a zero hub protrusion height. Protrusion height of hub 0.30Df 0.41Df 0.55Df 0.66Df Flow rate decrease rate 5% 15% 20% 22% (against maximum flow rate)

[0043] As shown in the graphs and tables, although a protruded hub decreases performance, abrupt performance decrease has almost nothing to do with hub shape, and it can noted that the abrupt performance decrease occurs where protrusion height (Hb) exceeds approximately 0.40 times the fan outer diameter (Df), and it is preferable to have a hub protrusion height (Hb) less than approximately 0.30 times the fan outer diameter (Df).

[0044] As apparent from the foregoing, there is an advantage in the multi-blade centrifugal fan thus described according to the present invention in that although a hub is mounted with a driving motor, an overall structural size is miniaturized to minimize a flow rate loss and to prevent a remarkable fan performance decrease. 

What is claimed is:
 1. A multi-blade centrifugal fan, the fan arranged with a plurality of blades in round shape and equipped with an end plate mounted with a tip end of the plurality of blades, wherein the end plate is centrally mounted with protruded hub toward an air intake, and here a protruded height (Hb) of the hub is less than 0.3 times the outer diameter (Df).
 2. The fan as defined in claim 1, wherein the hub is a conical shape having a narrow diameter at air intake.
 3. The fan as defined in claim 1, wherein the hub is shaped of a cylindrical form.
 4. The fan as defined in claim 1, wherein the hub is formed at lateral surfaces thereof with a plurality of holes for cooling the heat of a motor disposed at a space of the hub. 